Mueller has what's known as pectus excavatum, or the ribs and sternum are growing abnormally inward. This produces a caved-in or sunken appearance of the chest. It can either be present at birth or not develop until puberty. A surgical team inserted a steel rod through his chest two years ago, and added another one last year. But it hasn't stopped him from swimming and doing what he loves. It was hard at first, and had shortness of breath and other complications, but he says it's second nature to him now. The rods will come out eventually, he says, maybe next year.